Preparation method for ceramic composite material, ceramic composite material, and wavelength converter

ABSTRACT

Provided is a ceramic composite material and a wavelength converter. The ceramic composite material includes: an alumina matrix, a fluorescent powder uniformly distributed in the alumina matrix, and scattering centers uniformly distributed in the alumina matrix, wherein the alumina matrix is an alumina ceramics, the scattering centers are alumina particles, the alumina particles each have a particle diameter of 1 μm to 10 μm, and the fluorescent powder has a particle diameter of 13 μm to 20 μm.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/468,112, filed on Jun. 10, 2019, which is a national phase ofInternational Application No. PCT/CN2017/109317, filed on Nov. 3, 2017,which claims priority to and the benefit of CN 201611135583.4, filed onDec. 9, 2016. The disclosures of the above applications are incorporatedherein by reference.

FIELD

The present disclosure relates to the technical field of light-emittingmaterials, and in particular, to a method for preparing a ceramiccomposite material, a ceramic composite material as well as a wavelengthconverter.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

In the field of light-emitting display, a fluorescent powderencapsulation of a wavelength conversion device is mainly anencapsulation of an organic resin, an organic silica gel and aninorganic glass, and in such a technical solution, the wavelengthconversion device has the poor thermal conductivity and heat resistance.In order to solve this problem, it is known that the fluorescent powderand light-permeable inorganic ceramics are sintered together to obtain aceramic composite material, which has properties of excellent thermalconductivity and heat resistance.

At present, for the ceramic composite material in which the fluorescentpowder is encapsulated by Al₂O₃, it is a common problem that a weakbinding force between a fluorescent powder phase and an Al₂O₃ phase mayresult in poor mechanical performances. Moreover, most of ceramiccomposite materials also have problems such as low lighting effect,particles of the fluorescent powder being pulled out during processing,and difficulty in surface polishing, which may affect the performancesof the ceramic composite material.

SUMMARY

This section provides a general summary of the disclosure and is not acomprehensive disclosure of its full scope or all of its features.

The present disclosure aims to provide a method for preparing a ceramiccomposite material, which aims to obtain a ceramic composite materialhaving high lighting effect, high thermal conductivity and highmechanical performances.

In order to achieve the above-mentioned purpose, the ceramic compositematerial includes an alumina matrix, a fluorescent powder uniformlydistributed in the alumina matrix, and scattering centers uniformlydistributed in the alumina matrix, wherein the alumina matrix is analumina ceramics, the scattering centers are alumina particles, thealumina particles each have a particle diameter of 1 μm to 10 μm, andthe fluorescent powder has a particle diameter of 13 μm to 20 μm.

Optionally, the fluorescent powder comprises at least one Ce³⁺-dopedfluorescent powder selected from the group consisting of Ca₃Al₂Si₃O₁₂,Ca₃Sc₂Si₃O₁₂, Gd₃Al₅O₁₂, Gd₃Ga₅O₁₂, Tb₃Al₅O₁₂, Tb₃Ga₅O₁₂, Y₃Al₅O₁₂,Y₃Ga₅O₁₂, Lu₃Al₅O₁₂, Lu₃Ga₅O₁₂ and Y₃Mg₂AlSi₂O₁₂.

Optionally, the fluorescent powder has a particle diameter in a range of13 μm to 20 μm.

The present disclosure further provides a wavelength converter,including the ceramic composite material described above.

According to the technical solutions of the present disclosure, thefluorescent powder particles can be firstly coated with a small amountof Al₂O₃ particles having a small particle diameter (i.e., an Al₂O₃film) by means of liquid phase deposition, and then the obtained productis mixed with Al₂O₃ particles having a medium particle diameter andAl₂O₃ particles having a large particle diameter, so that the smallamount of Al₂O₃ particles having the small particle diameter and coatedon the fluorescent powder particle (i.e., an Al₂O₃ film) can be firsttransformed into a liquid phase during the sintering, thereby improvinga sinterability of the ceramic composite material, and effectivelyenhancing a bonding force between the fluorescent powder phase and theAl₂O₃ phase in the ceramic composite material. At the same time, throughthe dissolution and re-deposition mechanism, the abnormal growth of theAl₂O₃ particles having the medium particle diameter can be effectivelysuppressed during the sintering, thereby improving the performances ofthe Al₂O₃ matrix. The Al₂O₃ particles having the large particle diametercan be used as scattering particles in the ceramic composite material.In this way, a ceramic composite material having high lighting effect,high thermal conductivity, high mechanical performances, and adjustableblue light permeability can be prepared.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses. Itshould be understood that throughout the drawings, correspondingreference numerals indicate like or corresponding parts and features.

Technical solutions in the embodiments of the present disclosure will bedescribed in details as follow. It is obvious that the describedembodiments are merely parts of rather than all of the embodiments ofthe present disclosure. On basis of the embodiments described in thepresent disclosure, all other embodiments obtained by those skilled inthe art without creative efforts shall fall within the protection scopeof the present disclosure.

In addition, the technical solutions in individual embodiments can becombined with each other under a premise of realizability for thoseskilled in the art. If a combination of technical solutions iscontradictory or impossible to implement, it should be considered thatthe combination of technical solutions does not exist and shall not fallwithin the protection scope of the present disclosure.

The present disclosure provides a method for preparing a ceramiccomposite material, in order to prepare a ceramic composite materialhaving high lighting effect, thermal conductivity, mechanicalperformances and adjustable blue light permeability, which the ceramiccomposite can be applied to a laser light source having a highperformance.

The method for preparing the ceramic composite material includes thefollowing steps.

In step S100, an aluminum salt solution and a fluorescent powder areprepared according to a mass ratio of Al₂O₃ to fluorescent powder of(0.1 to 1):100.

In this step, the fluorescent powder is a Ce³⁺-doped fluorescent powderselected from at least one of Ca₃Al₂Si₃O₁₂, Ca₃Sc₂Si₃O₁₂, Gd₃Al₅O₁₂,Gd₃Ga₅O₁₂, Tb₃Al₅O₁₂, Tb₃Ga₅O₁₂, Y₃Al₅O₁₂, Y₃Ga₅O₁₂, Lu₃Al₅O₁₂,Lu₃Ga₅O₁₂ and Y₃Mg₂AlSi₂O₁₂. Moreover, the fluorescent powder has aparticle diameter in a range of 13 μm to 20 μm, preferably 15 μm to 17μm.

A concentration of the aluminum salt solution is in a range of 0.01mol/L to 1 mol/L, preferably 0.2 mol/L to 0.5 mol/L.

An aluminum nitrate solution can be used as the aluminum salt solution.

It should be understood that, when actually preparing the aluminum saltsolution and the fluorescent powder, a mass ratio of Al₂O₃ to thefluorescent powder is firstly determined, and then a certain mass of thefluorescent powder is weighted; according to the mass of the fluorescentpowder and the mass ratio of Al₂O₃ to the fluorescent powder, a requiredmass of the Al₂O₃ is calculated, and thus a mole number of Al³⁺ can beobtained by conversion; a corresponding mass of aluminum salt can becalculated according to the mole number of Al³⁺; and finally, thecorresponding mass of aluminum salt is weighted to prepare the aluminumsalt solution. In this way, the aluminum salt solution and thefluorescent powder are prepared, respectively.

In step S200, the fluorescent powder is dispersed in a buffer solutionhaving a pH 4.5 to 5.5 to obtain a suspension. In this step, a citricacid-sodium hydroxide solution can be used as the buffer solution, andthe citric acid-sodium hydroxide solution includes citric acid with aconcentration in a range of 0.8 mol/L to 1.2 mol/L.

In addition, before dispersing the fluorescent powder in the buffersolution, 1 wt % to 3 wt % of PEG 4000 is pre-added into the buffersolution.

In step S300, the suspension is titrated with the aluminum salt solutionto obtain a fluorescent powder coated with an Al₂O₃ hydrate film.

In this step, during the process of titrating, the suspension has atemperature in a range of 40° C. to 70° C., and a stirring rate is in arange of 100 r/min to 300 r/min, and a titrating rate is in a range of 5mL/min to 50 mL/min.

After the titrating, the above temperature and stirring are maintainedfor 1 h to 2 h, following by adjusting the pH value into a range of 6 to7 with a sodium hydroxide solution.

In step S400, the fluorescent powder coated with the Al₂O₃ hydrate filmis calcined to obtain an Al₂O₃-coated fluorescent powder.

Before the calcining, the step includes:

Centrifuging the fluorescent powder coated with the Al₂O₃ hydrate film;

Washing the obtained fluorescent powder coated with the Al₂O₃ hydratefilm with water and dehydrating for 3 to 5 times, and then drying at atemperature in a range of 75° C. to 85° C.

During the calcining, a calcination temperature is in a range of 300° C.to 600° C., and a calcination duration is in a range of 2 h to 5 h.

It should be noted that, at this moment, the surface of the fluorescentpowder is coated with Al₂O₃ particle having a small particle diameter.

In step S500, an alumina powder having a particle diameter of 0.1 μm to1 μm and an alumina powder having a particle diameter of 1 μm to 10 μmare mixed according to a molar ratio of 100:(0.1 to 5), so as to obtaina mixed alumina powder.

In this step, the alumina powder having a particle diameter of 0.1 μm to1 μm (i.e., Al₂O₃ particles having a medium particle diameter)preferably has a particle diameter from 0.1 μm to 0.3 μm.

The alumina powder having a particle diameter of 1 μm to 10 μm (i.e.,the Al₂O₃ particles having a large particle diameter) preferably has aparticle diameter from 3 μm to 5 μm.

Further, an alumina powder having a particle diameter of 0.01 μm to 0.1μm, preferably a particle diameter of 0.02 μm to 0.05 μm may also beadded into the mixed alumina powder, and a molar ratio of the aluminumpowder having a particle diameter of 0.01 μm to 0.1 μm to the aluminapowder having a particle diameter of 0.1 μm to 1 μm is (0.1-1):100.

In step S600, the Al₂O₃-coated fluorescent powder and the mixed aluminapowder are mixed to obtain a mixed powder, in which the Al₂O₃-coatedfluorescent powder accounts for 40% to 90% by weight of the mixedpowder.

Preferably, the Al₂O₃-coated fluorescent powder accounts for 50% to 70%by weight of the mixed powder.

The step of mixing the Al₂O₃-coated fluorescent powder and the mixedalumina powder includes:

Dispersing the mixed alumina powder into a PEG 4000-ethanol solutionhaving a concentration of 1% to 3% by weight, and placing them into aball-milling tank to perform ball-milling for 6 h to 24 h;

Adding the Al₂O₃-coated fluorescent powder into the ball-milling tank tofurther perform the ball-milling for 30 min to 60 min.

In step S700, the mixed powder is pre-pressed and sintered, so as toobtain the ceramic composite material.

The pre-pressing is carried out under a pressure of 5 MPa to 15 MPa.

The sintering is carried out in an argon atmosphere, a sinteringtemperature is in a range of 1250° C. to 1550° C., a holding time is ina range of 30 min to 360 min, and a sintering pressure is in a range of30 MPa to 200 MPa. Here, the sintering pressure is preferably in a rangeof 40 MPa to 100 MPa.

It should be noted that, by properly controlling the sinteringtemperature during the sintering process, the Al₂O₃ particles having asmall particle diameter and the Al₂O₃ particles having a medium particlediameter can be completely transformed into a liquid phase to besintered, and the Al₂O₃ particles having a large particle diameter arepartially or not sintered, while the fluorescent powder is not sintered.Here, a grain form and grain particle diameter of the fluorescent powderdo not change. A grain form of the Al₂O₃ particles having the largeparticle diameter turns to a phase from another phase, and a diameterthereof increases due to a dissolution and re-deposition mechanism.

The dissolution and re-deposition mechanism in the technical solution ofthe present disclosure is as follows, during the sintering process, theAl₂O₃particles having the small particle diameter are transformed intothe liquid phase and fully melted, and then the Al₂O₃ particles havingthe medium particle diameter are partially transformed into the liquidphase. Here, the smaller the particle diameter of the particles is, theeasier they can be transformed into a liquid phase. The liquid phaseflows in spaces between particles, which is a main way of materialmigration. When the liquid phase flows over the surface of largeparticles, small Al₂O₃ grains are deposited on the surfaces. It shouldbe noted that, the small Al₂O₃ grains are also possible to be depositedon the surface of small particles, but the deposition on the surface oflarge particles has a greater possibility and a greater degree). In thiscase, the participated small Al₂O₃ grains are classified into two types.

A first type is that the small Al₂O₃ grains are deposited on thesurfaces of the fluorescent powder particles, since the fluorescentpowder is not involved in the sintering, the deposited small Al₂O₃grains and the adjacent Al₂O₃ grains go through a process ofjointing-fusing-growing via a sintering neck and become an alumina phaseclosely attached to the fluorescent powder particles.

A second type is that the small Al₂O₃ grains are deposited on thesurfaces of the Al₂O₃ particles having the large particle diameter, anda part of the small Al₂O₃ grains is attached to the Al₂O₃ particleshaving the large particle diameter to an extent depending upon theactual temperature, so as to become large particles while absorbing alot of energy. The continuous growing of the Al₂O₃ particles having thelarge particle diameter actually suppresses an abnormal growth of theAl₂O₃ particles having the medium particle diameter, thereby promotinggrowth uniformity of the majority of the Al₂O₃ particles having themedium particle diameter. In this way, the optical performances andmechanical performances can be effectively improved.

In the sintered ceramics, the Al₂O₃ particles having the small particlediameter and the Al₂O₃ particles having the medium particle diameterform a continuous matrix of ceramics having a certain lightpermeability, while the fluorescent powder and the Al₂O₃ particleshaving the large particle diameter act as the particles dispersed in thecontinuous matrix of ceramics and having a scattering effect. Here, thefluorescent powder absorbs the blue light having a short wavelength suchas 445 nm to 460 nm, and the Al₂O₃ particles having the large particlediameter have a scattering and reflection effect on light having awavelength in a range of a short wavelength to a visible lightwavelength. Moreover, by adjusting a concentration of the Al₂O₃particles having the large particle diameter, the permeability and thescattering degree of the blue light can be changed, thereby changing acolor temperature of the ceramic composite material.

Therefore, it can be understood that, according to the technicalsolution of the present disclosure, the fluorescent powder particles arefirstly coated with a small amount of Al₂O₃ particles having the smallparticle diameter (i.e., an Al₂O₃ film) by means of liquid phasedeposition, and the obtained product is mixed with Al₂O₃particles havingthe medium particle diameter and Al₂O₃ particles having the largeparticle diameter, so that the small amount of Al₂O₃ particles havingthe small particle diameter and coated on the fluorescent powderparticle (i.e., the Al₂O₃ film) can be first transformed into a liquidphase during the sintering, thereby improving a sinterability of theceramic composite material, and effectively enhancing a bonding forcebetween the fluorescent powder phase and the Al₂O₃ phase in the ceramiccomposite material. At the same time, through the dissolution andre-deposition mechanism, the abnormal growth of the Al₂O₃ particleshaving the medium particle diameter can be effectively suppressed duringthe sintering, thereby improving the performances of the Al₂O₃ matrix.In the meantime, the Al₂O₃ particles having the large particle diametercan be used as scattering particles in the ceramic composite material.In this way, a ceramic composite material having high lighting effect,thermal conductivity, mechanical performances, and adjustable blue lightpermeability can be prepared.

The technical solutions of the present disclosure will be describedthrough specific embodiments as below.

EMBODIMENT 1

An appropriate amount of YAG:Ce³⁺ fluorescent powder having a particlediameter of 13 μm to 20 μm is weighted.

According to a mass ratio of Al₂O₃ to YAG:Ce³⁺ fluorescent powder of1:100, a corresponding amount of Al(NO₃)₃.9H₂O is weighted to prepare analuminum nitrate solution with a concentration of 1 mol/L.

A citric acid-sodium hydroxide solution with a pH value of 5.0 and aconcentration of 1.0 mol/L is prepared, and then 2 wt % of PEG 4000 isadded thereto and dissolved through ultrasonic. Thereafter, YAG:Ce³⁺fluorescent powder is added, and after ultrasonic dispersion, themixture is provided with a magnetic stirrer and placed on a magneticstirring device to be evenly stirred, so as to obtain a fluorescentpowder suspension.

The fluorescent powder suspension is heated up to 50° C., andcontinuously stirred with a stirring rate of 150 r/min, and then thefluorescent powder suspension is titrated with the aluminum nitratesolution at a constant rate of 30 mL/min by using a dropper. After thetitration, the temperature and stirring are maintained for 1 h, and thenthe pH value is adjusted to 6.5 with a sodium hydroxide solution, so asto obtain a YAG:Ce³⁺ fluorescent powder coated with an Al₂O₃ hydratefilm.

The YAG:Ce³⁺ fluorescent powder coated with the Al₂O₃ hydrate film iscentrifuged, washed with water, dehydrated three times, dried at 80° C.,and then calcined at 500° C. for 5 h, so as to obtain an Al₂O₃-coatedYAG:Ce³⁺ fluorescent powder.

An ultrafine Al₂O₃ powder with a high purity (having a particle diameterof 0.1 μm to 1 μm) and an Al₂O₃ powder with a high purity (having aparticle diameter of 1 μm to 10 μm) are mixed according to a molar ratioof 100:1, so as to obtain a mixed Al₂O₃ powder.

1 wt % of PEG 4000-ethanol solution is prepared, and then the mixedAl₂O₃ powder is added thereto. After ultrasonic dispersion, the mixtureis placed into a teflon ball-milling tank and an appropriate amount ofhigh-purity zirconia balls are added in the ball-milling tank,performing the ball-milling for 12 h. Thereafter, the Al₂O₃-coatedYAG:Ce³⁺ fluorescent powder, which accounts for 50% of the total weightof the powder, is added to the ball-milling tank, followed by performingthe ball-milling for 40 min.

A slurry obtained after the ball-milling is vacuum dried, pulverized,and sieved, so as to obtain a mixed powder.

An appropriate amount of the mixed powder is weighted, placed into agraphite mold and pre-pressed under a pressure of 10 MPa. Thereafter,the graphite mold is placed into a hot and pressured sintering furnaceand maintained for 60 min in an argon atmosphere, at a sinteringtemperature of 1250° C., and a sintering pressure of 100 MPa.

After the sintering, the pressure is removed and the mold is cooledtogether with the furnace, so as to obtain a ceramic composite materialYAG:Ce⁺—Al₂O₃.

EMBODIMENT 2

An appropriate amount of YAG:Ce³⁺ fluorescent powder having a particlediameter of 13 μm to 20 μm is weighted.

According to a mass ratio of Al₂O₃ to YAG:Ce³⁺ fluorescent powder of1:1000, a corresponding amount of Al(NO₃)₃.9H₂O is weighted to preparean aluminum nitrate solution with a concentration of 0.5 mol/L.

A citric acid-sodium hydroxide solution with a pH value of 5.0 and aconcentration of 1.0 mol/L is prepared, and then 3 wt % of PEG 4000 isadded thereto and dissolved through ultrasonic. Thereafter, YAG:Ce³⁺fluorescent powder is added, and after ultrasonic dispersion, themixture is provided with a magnetic stirrer and placed on a magneticstirring device to be evenly stirred, so as to obtain a fluorescentpowder suspension.

The fluorescent powder suspension is heated up to 65° C., andcontinuously stirred with a stirring rate of 280 r/min, and then thefluorescent powder suspension is titrated with the aluminum nitratesolution at a constant rate of 45 mL/min by using a dropper. After thetitration, the temperature and stirring are maintained for 1 h, and thenthe pH value is adjusted to 7.0 with a sodium hydroxide solution, so asto obtain a YAG:Ce³⁺ fluorescent powder coated with an Al₂O₃ hydratefilm.

The YAG:Ce³⁺ fluorescent powder coated with the Al₂O₃ hydrate film iscentrifuged, washed with water, dehydrated three times, dried at 85° C.,and then calcined at 320° C. for 5 h, so as to obtain an Al₂O₃-coatedYAG:Ce³⁺ fluorescent powder.

An ultrafine Al₂O₃ powder with a high purity (having a particle diameterof 0.01 μm to 0.1 μm), an ultrafine Al₂O₃ powder with a high purity(having a particle diameter of 0.1 μm to 1 μm) and an Al₂O₃ powder witha high purity (having a particle diameter of 1 μm to 10 μm) are mixedaccording to a molar ratio of 1:100:3, so as to obtain a mixed Al₂O₃powder.

2 wt % of PEG 4000-ethanol solution is prepared, and then the mixedAl₂O₃ powder is added thereto. After ultrasonic dispersion, it is placedinto a teflon ball-milling tank, and then an appropriate amount ofhigh-purity zirconia balls are added in the ball-milling tank,performing the ball-milling for 24 h. Thereafter, the Al₂O₃-coatedYAG:Ce³⁺ fluorescent powder, which accounts for 70% of the total weightof the powder, is added to the ball-milling tank, followed by performingthe ball-milling for 60 min.

A slurry obtained after the ball-milling is vacuum dried, pulverized,and sieved, so as to obtain a mixed powder.

An appropriate amount of the mixed powder is weighted, placed into agraphite mold and pre-pressed under a pressure of 15 MPa. Thereafter,the graphite mold is placed into a hot and pressured sintering furnaceand maintained for 300 min in an argon atmosphere, at a sinteringtemperature of 1500° C., and a sintering pressure of 60 MPa.

After the sintering, the pressure is removed and the mold is cooledtogether with the furnace, so as to obtain a ceramic composite materialYAG:Ce³⁺—Al₂O₃.

EMBODIMENT 3

An appropriate amount of LuAG:Ce³⁺ fluorescent powder having a particlediameter of 13 μm to 20 μm is weighted.

According to a mass ratio of Al₂O₃ to LuAG:Ce³⁺ fluorescent powder of1:500, a corresponding amount of Al(NO₃)₃.9H₂O is weighted to prepare analuminum nitrate solution with a concentration of 0.3 mol/L.

A citric acid-sodium hydroxide solution with a pH value of 5.0 and aconcentration of 1.0 mol/L is prepared, and then 1 wt % of PEG 4000 isadded thereto and dissolved through ultrasonic. Thereafter, LuAG:Ce³⁺fluorescent powder is added, and after ultrasonic dispersion, themixture is provided with a magnetic stirrer and placed on a magneticstirring device to be evenly stirred, so as to obtain a fluorescentpowder suspension.

The fluorescent powder suspension is heated up to 40° C., andcontinuously stirred with a stirring rate of 110 r/min. Thereafter, thefluorescent powder suspension is titrated with the aluminum nitratesolution at a constant rate of 15 mL/min by using a dropper. After thetitration, the temperature and stirring are maintained for 1 h, and thenthe pH value is adjusted to 7.0 with a sodium hydroxide solution, so asto obtain a LuAG:Ce³⁺ fluorescent powder coated with an Al₂O₃ hydratefilm.

The LuAG:Ce³⁺ fluorescent powder coated with the Al₂O₃ hydrate film iscentrifuged, washed with water, dehydrated four times, dried at 80° C.,and then calcined at 300° C. for 5 h, so as to obtain an Al₂O₃-coatedLuAG:Ce³⁺ fluorescent powder.

An ultrafine Al₂O₃ powder with a high purity (having a particle diameterof 0.1 μm to 1 μm) and an Al₂O₃ powder with a high purity (having aparticle diameter of 1 μm to 10 μm) are mixed according to a molar ratioof 20:1, so as to obtain a mixed Al₂O₃ powder.

3 wt % of PEG 4000-ethanol solution is prepared, and then the mixedAl₂O₃ powder is added thereto. After ultrasonic dispersion, the mixtureis placed into a teflon ball-milling tank, and then an appropriateamount of high-purity zirconia balls are added in the ball-milling tank,performing the ball-milling lasts for 8 h. Thereafter, the Al₂O₃-coatedLuAG:Ce³⁺ fluorescent powder, which accounts for 45% of the total weightof the powder, is added to the ball-milling tank, followed by performingthe ball-milling for 30 min.

A slurry obtained after the ball-milling is vacuum dried, pulverized,and sieved, so as to obtain a mixed powder.

An appropriate amount of the mixed powder is weighted, placed into agraphite mold and pre-pressed under a pressure of 5 MPa. Thereafter, thegraphite mold is placed into a hot and pressured sintering furnace andmaintained for 180 min in an argon atmosphere, at a sinteringtemperature of 1300° C., and a sintering pressure of 50 MPa.

After sintering, the pressure is removed and the mold is cooled togetherwith the furnace, so as to obtain a ceramic composite materialLuAG:Ce³⁺—Al₂O₃.

It should be noted that, during the preparation of the ceramic compositematerial with the processes described in Embodiments 1 to 3, a ternarysystem of the alumina particles facilitates the sintering process of theceramic composite material. In the ternary system, the small aluminaparticles can serve as a co-solvent, and the large alumina particles cannot only improve a filling efficiency during powder filling, butameliorate liquid phase sintering and prevent the abnormal growth ofgrains during the sintering. Moreover, the large alumina particles alsohas a scattering effect on light, and the light permeability and lightreflectivity of the ceramic composite material with respect to theexcited blue light can be changed by adjusting the amount of largealumina particles, thereby adjusting a color temperature of the ceramiccomposite material. Moreover, during the sintering, the ternary systemalso contributes to improving the bonding between the fluorescent powderparticle and the alumina matrix, thereby improving the mechanicalperformances of the ceramic composite material.

Therefore, by preparing the ceramic composite material with theprocesses described in Embodiments 1 to 3, the ceramic composite canhave high lighting effect, thermal conductivity, mechanicalperformances, and adjustable blue light permeability, and thus can beapplied to a laser source having a high performance, especially aminiaturized laser source system.

The present disclosure further provides a ceramic composite materialincluding an alumina matrix, a fluorescent powder uniformly distributedin the alumina matrix, and scattering centers uniformly distributed inthe alumina matrix. The alumina matrix is a continuous alumina ceramics,the scattering centers are alumina particles, the alumina particles eachhave a particle diameter in a range of 1 μm to 10 μm, and thefluorescent powder has a particle diameter in a range of 13 μm to 20 μm.

The ceramic composite material has high temperature resistance, goodthermal conductivity, and excellent mechanical performances.

The present disclosure further provides a wavelength converter,including the ceramic composite material as described above. Since thewavelength converter adopts all the technical solutions described in theabove embodiments, it possesses at least all the beneficial effects ofthe technical solutions described in the above embodiments, which willnot be repeatedly described herein. The wavelength converter can beapplied in a stationary installation environment, as well as in a movingdevice (such as a wavelength conversion color wheel). The wavelengthconverter can be applied to the lighting field, for example, variouslighting devices such as a street lamp, a searchlight, a stage light,and a car headlight. The wavelength converter can also be applied to adisplay system, such as a projector, a televisions, etc., and satisfyall requirements thereof.

The above description is merely preferred embodiments of the presentdisclosure, but not intended to limit a scope of the present disclosure.Under the concepts of the present disclosure, any equivalent structuralsubstitution or any direct/indirect application in other relevanttechnical fields shall fall within the patent protection scope of thepresent disclosure.

Unless otherwise expressly indicated herein, all numerical valuesindicating mechanical/thermal properties, compositional percentages,dimensions and/or tolerances, or other characteristics are to beunderstood as modified by the word “about” or “approximately” indescribing the scope of the present disclosure. This modification isdesired for various reasons including industrial practice, material,manufacturing, and assembly tolerances, and testing capability.

As used herein, the phrase at least one of A, B, and C should beconstrued to mean a logical (A OR B OR C), using a non-exclusive logicalOR, and should not be construed to mean “at least one of A, at least oneof B, and at least one of C.”

The description of the disclosure is merely exemplary in nature and,thus, variations that do not depart from the substance of the disclosureare intended to be within the scope of the disclosure. Such variationsare not to be regarded as a departure from the spirit and scope of thedisclosure.

What is claimed is:
 1. A ceramic composite material, comprising analumina matrix, a fluorescent powder uniformly distributed in thealumina matrix, and scattering centers uniformly distributed in thealumina matrix, wherein the alumina matrix is an alumina ceramics, thescattering centers are alumina particles, the alumina particles eachhave a particle diameter of 1 μm to 10 μm, and the fluorescent powderhas a particle diameter of 13 μm to 20 μm.
 2. The ceramic compositematerial according to claim 1, wherein the fluorescent powder comprisesat least one Ce³⁺-doped fluorescent powder selected from the groupconsisting of C₃Al₂Si₃O₁₂, Ca₃Sc₂Si₃O₁₂, Gd₃Al₅O₁₂, Gd₃Ga₅O₁₂,Tb₃Al₅O₁₂, Tb₃Ga₅O₁₂, Y₃Al₅O₁₂, Y₃Ga₅O₁₂, Lu₃Al₅O₁₂, Lu₃Ga₅O₁₂ andY₃Mg₂AlSi₃O₁₂.
 3. The ceramic composite material according to claim 1,wherein the particle diameter of the fluorescent powder is 15 μm to 17μm.
 4. A wavelength converter comprising the ceramic composite materialaccording to claim 1.